An electrophotographic photoreceptor generally is formed by joining flanges or gear flanges at both ends of a photosensitive drum configured from a conductive base having an outer peripheral face provided with a photosensitive layer. Such a photoreceptor is mounted in a process cartridge, and is further installed into a photocopier, printer, fax machine, or other electrophotography application device for use.
A process cartridge incorporates into an integrated cartridge, disposed close to an electrophotographic photoreceptor, a charging member for directly applying a voltage (including discharging) and various members necessary for development, cleaning, and other electrophotography processes. The cartridge is removably installed in an electrophotography application device, and performs vital functions for image formation.
In an electrophotography application device with a process cartridge installed, first a latent image is formed by optical exposure corresponding to image information of the electrophotographic photoreceptor, which is uniformly charged by a charging process. Next, this latent image is developed using toner in a development process, to form a toner image on the photoreceptor. Then, this toner image is transferred onto paper or another supporting medium by a transfer process, to form an image.
In the prior art, process cartridge methods like that described above have been widely adopted in electrophotography application devices using electrophotography processes. By means of such process cartridges, maintenance of the device main unit is rendered substantially unnecessary, and there is the advantageous result that device maintenance becomes extremely simple.
However, in a process cartridge the electrophotographic photoreceptor executes electrophotography processes by receiving a rotational driving force from the device main unit and rotating. Hence in order to transmit the driving force, a flange or a flange comprising a gear is generally joined to an end portion of the photosensitive drum.
If the gear flange or the flange joined to the photosensitive drum should separate from the photoreceptor, or the joining portion should loosen, a driving force is not transmitted and rotation of the photoreceptor stops, and a major accident such as halting of the device function, or the jitter or other image defects occurs. Hence securing long-term reliability at the portion joining the gear flange or flange to the photosensitive drum such that separation or loosening does not occur is an important technical problem.
On the other hand, in cases where the precision of fit of the driven-side power transmission portion of the flange and the driving-side power transmission portion of the device main unit is poor, problems with transmission of driving force occur, possibly leading to the occurrence of image defects. Hence in addition to securing reliable joining of the flange with the photosensitive drum, it is also important that high rotation precision be maintained over the long term by optimizing the fitting state of the driving-side power transmission portion and reliably transmitting rotational driving force.
To improve the driven-side power transmission portion of the flange, for example Patent Reference 1 discloses a technique wherein a prescribed crooked hole is provided in a device main unit gear, and moreover a twisting protrusion is provided in one end in the length direction of the electrophotographic photoreceptor drum, and that through the fitting of these to transmit a rotational driving force, the rotational precision of the photoreceptor drum is improved.
Further, Patent Reference 2 discloses a technique wherein a device main unit and a process cartridge are respectively provided with a conjoining hole and conjoining protrusion formed on a gear on the device main unit side, and a protruding portion and abutting portion circumscribing same, and wherein by conjoining the device main unit and the process cartridge by means thereof, reliable transmission of driving force and prevention of process cartridge vibration are achieved.
Further, Patent Reference 3 discloses a technique relating to a developing cylinder and driving gear with improved shapes of the driven-side power transmission portions, in order to quickly performing molding machining relating to the flange driven-side power transmission portion.
Patent Reference 1: Japanese Patent Application Laid-open No. H8-328449 (Scope of Claims and similar)
Patent Reference 2: Japanese Patent Application Laid-open No. 2001-423845 (Scope of Claims and similar)
Patent Reference 3: U.S. Pat. No. 6,173,146 (Specification)
As described above, various studies relating to the structure of the driven-side power transmission portion of flanges have been made to date; but there is still a need for a flange with heightened practical applicability, achieved by increasing the rotational transmitted force during driving and improving the long-term reliability of the rotational precision, as well as improving cost-efficiency.
Further, because the direction of rotation of the driving-side power transmission portion of the device main body differs with the specifications of the device main body of the electrophotography application device, the shapes of the driving-side power transmission portion and of the driven-side power transmission portion must be changed according to the rotation direction. Hence a plurality of types of driven-side power transmission portions must be fabricated according to the shape of the driving-side power transmission portion, and there is a need for a driven-side power transmission portion which affords compatibility and is durable.